1. Field of the Invention (Technical Field)
The present invention relates to apparatuses and methods for remotely detecting concealed weapons.
2. Background Art
There are no known weapons detection systems on the market today that can detect a concealed weapon from a distance of more than three feet. Virtually every device in operation is an electromagnetic device that requires the use of a portal. An eddy current flows through the portal and when metallic objects create a change in the magnetic flux, it activates a warning signal. This type of system cannot discriminate between concealed weapons and other metallic objects such as belt buckles, jewelry, coins, watches, or calculators.
Millitech Corporation of South Deerfield, Mass., may be developing a passive millimeter system. The system apparently would require the use of a portal, a floor plate, a video camera and a cathode ray tube to view the area being searched. Millitech has claimed it was developing a 300 mm aperture camera for fixed entrance-way surveillance to demonstrate their technology. The company claims its passive millimeter wave imagers will not require the subject to be exposed to any man-made electromagnetic fields or other radiation from an imaging system.
Likewise, Demma et al. utilizes millimeter-wave efforts but has not been able to detect non-metallic objects successfully. They also have limited ranging, being effective only to 2 meters. Infrared technologies, covered extensive in Demma et al., have great difficulty penetrating layers of clothing. In addition, in warmer climates, a gun carried on the body will take on the same temperatures as the body, making infrared virtually useless.
The Raytheon Company of Portsmouth, R.I., bases its weapons detection system on low frequency electromagnetic radiation. Their concept is based on illuminating the subject with a low intensity electromagnetic pulse known as a Heaviside pulse and measuring the time decay of the reradiated energy from metal objects carried by the person. The intensity and the time decay of the secondary radiation can be characterized and the signatures identified as a gun or non-threatening metal objects.
Idaho National Engineering Laboratory uses technology based on passive sampling of the earth""s magnetic field. Local aberrations in the magnetic field are produced by ferromagnetic objects such as guns and knives. In the gun detection system being developed by Idaho National Engineering Laboratory, the magnetic aberrations or anomalies were to be sensed and measured by magnetic gradiometers. They were planning to construct a scanner using a multiple magnetometer design that could be a standalone unit, much like an airport scanner system. The scanner would be triggered electronically by a threshold detector. Data would be collected simultaneously from all sensors in the system providing a top to bottom magnetic profile of the targeted person. Reasonable suspicion about the presence of a concealed weapon would be dictated by the location and magnitude of magnetic anomalies.
Other attempts to provide a useful weapons detection system (or solve some marginally related detection problem) include U.S. Pat. No. 5,552,705, entitled xe2x80x9cNon-Obstrusive Weapon Detection System and Method for Discriminating Between a Concealed Weapon and Other metal Objects,xe2x80x9d to Keller; U.S. Pat. No. 5,519,400, entitled xe2x80x9cPhase Coded, Micro-Power Impulse Radar Motion Sensor,xe2x80x9d to McEwan; U.S. Pat. No. 5,512,834, entitled xe2x80x9cHomodyne IMpulse Radar Hidden Object Locator,xe2x80x9d to McEwan; U.S. Pat. No. 5,457,394, entitled xe2x80x9cImpulse Radar Studfinder,xe2x80x9d to McEwan; U.S. Pat. No. 5,381,153, entitled xe2x80x9cPortable FM-CW Radar Device with Frequency Conversion by First and Second Frequencies,xe2x80x9d to Saito et al.; U.S. Pat. No. 5,365,237, entitled xe2x80x9cMicrowave Camera,xe2x80x9d to Johnson et al.; U.S. Pat. No. 5,345,240, entitled xe2x80x9cHandheld Obstacle Penetrating Motion Detecting Radar,xe2x80x9d to Frazier; U.S. Pat. No. 5,337,053, entitled xe2x80x9cMethod and Apparatus for Classifying Targets,xe2x80x9d to Dwyer; U.S. Pat. No. 5,334,981, entitled xe2x80x9cAirborne Metal Detecting Radar,xe2x80x9d to Smith et al.; U.S. Pat. No. 4,905,008, entitled xe2x80x9cRadar Type Underground Searching Apparatus,xe2x80x9d to Kawano et al.; U.S. Pat. No. 3,707, 672, entitled xe2x80x9cWeapon Detector Utilizing the Pulsed Field Technique to Detect Weapons on the Basis of Weapons Thickness,xe2x80x9d to Miller et al.; and Demma et al., entitled xe2x80x9cRemote Concealed Weapon Detection by Electromagnetic Imaging Techniques.xe2x80x9d
Miller and Keller employ magnetic field sensors and so will not detect guns made of non-magnetic materials such as aluminum, brass, and copper. McEwan ""400 employs monodyne impulse radar and cannot discriminate between object types. McEwan ""834 and ""394 employ impulse radars to locate large objects behind dielectric media and do not attempt to identify objects detected. Saito et al. employs Doppler radar to determine existence and motion of an object, but not the nature of the object. Johnson et al. is essentially a microwave ultrasound imager and does not measure or examine backscatter. Frazier is a conventional moving target indicator (MTI) radar. Dwyer does analyze radar backscattering but does so with respect to unobstructed objects, not concealed ones. Smith et al. uses radar cross polarization scattering for camouflaged metal detection, but does not rely on spectral content. Kawano et al. is a simple radar system for seeking objects or pockets below ground.
The present invention solves the deficiencies of the prior art. It illuminates a subject with a low intensity short pulse radar. Objects made of metal or high dielectric constant non-conductive material are nearly all backscattered. If a handgun is present, a unique spectral signature is received. Signatures can be prestored or learned by a computer employing artificial intelligence techniques.
The invention has an operating distance of at least between four yards to 20 yards. The invention, in its portable, hand-held form, is useful by law enforcement agencies, correctional facilities, the military and private security companies in the United States and throughout the world. The door-mounted embodiment is useful by federal, state and local governments, as well as financial institutions, convenience stores and other retail businesses, airports, schools and owners of private office and apartment buildings. Each of these entities has a critical need for a low-cost, highly dependable weapons detection system. The Bureau of Alcohol, Tobacco and Firearms estimates there are between 60 million to 200 million firearms in the United States today. More than 65,000 people were killed by firearms in the United States between 1988 and 1992. In 1993, homicides were the second leading cause of job-related fatalities in the United States, following only highway accidents. In 1993, the Federal Bureau of Investigation reported there were 11,876 bank robberies in the United States, resulting in a loss of $39.3 million. There were almost 35,000 armed robberies to convenience stores in the United States, accounting for a $15.7 million loss. In addition, the National Education Association reports an estimated 100,000 students carry a gun to school. Gunshots now cause one in every four deaths among American teenagers. Other countries are facing similar problems. The present invention seeks to lower these appalling statistics.
The present invention is directed to a weapons detection system. The preferred weapons detector comprises: a transmitter for producing an output of frequencies of a set of self-resonant frequencies of weaponry; an antenna directing the transmitter output toward locations potentially having weaponry and collecting backscattered signals; a receiver receiving the backscattered signals and operating over a range of the self-resonant frequencies; and a signal processor for detecting presence of a plurality of the self-resonant frequencies in the backscattered signals.
A range finder is preferably used for normalizing the backscattered signals. The transmitter preferably produces an output of frequencies between approximately 1 GHz and approximately 10 Ghz. The time resolution of the receiver is preferably less than approximately 10 nanoseconds. The minimum signal detection capability of the receiver is preferably less than approximately 1 millivolt.
The weapons detector makes a prediction about presence of weaponry on a human body. The accuracy is better than or equal to approximately 75%, preferably better than or equal to approximately 95%, and most preferably better than or equal to approximately 98%. Accuracies of 99.75% have been obtained.
The weapons detector may be portable, hand-held, mounted on a wall or in a doorway. Weaponry is detected preferably between 3-20 yards and most preferably between 4-15 yards. Upon detection, the doorway could be activated (e.g., to lock) or a camera could take a picture of the suspect.
A neural network is preferably utilized in the signal processor to aid in detection. The neural network is trained to recognize backscattered signals from weaponry prior to field use.
Preferably, the weapons detector provides a result within approximately one second of transmitter output. The weapons detector can indicate presence and absence of weaponry. Possible indicators are: audible signals, silent signals, tactile signals, visual signals, mechanical signals, and displayed messages. The weapons detector is useful for detecting weaponry such as handguns, rifles, shotguns, and pipe bombs. The weapons detector is also useful for discerning weaponry from objects such as belt buckles, bracelets, wristwatches, tape recorders, soft drink cans, coins, calculators, lipstick holders, calculators, campaign buttons, cellular telephones, key rings, keys and the like. Weaponry can be detected in or under clothing or accessories such as purses, belts, holsters, pants, briefcases, coats and shirts.
Principal objects of the present invention are to detect concealed weapons with a high accuracy (i.e., 98%), a one second response time or better, portability, an effective operating range (e.g., four to 15 yards, equivalent to the distance of a typical traffic stop, or more (up to fifty yards)), limited operational complexity, and high durability.
Another object of the invention is to provide a door model able to cover an area approximately three yards by five yards or better around an entrance.
Other objects, advantages and novel features, and further scope of applicability of the present invention will be set forth in part in the detailed description to follow, taken in conjunction with the accompanying drawings, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.